Work has been carried out on a number of structural problems related to proteins derived from the HIV-1 virus. The three dimensional solution structure of the complete ectodomain of SIV gp41 was determined and refined. In addition, the structure of a variant of the HIV-1 integrase N-terminal domain complexed with Cd instead of the naturally occuring Zn was solved. Based on the NMR structure of cyanovirin-N, the X- ray structure of this protein was solved. In addition, novel methodological approaches for improving the accuracy of NMR structures using residual dipolar couplings were developed and applied to a variety of systems. - Integrase, gp41, cyanovirin-N, NMR structures.